JP5217643B2 - Pinion shaft support structure of rack and pinion type steering device - Google Patents

Description

  The present invention relates to a rack and pinion type steering device for a vehicle, and more particularly to a pinion shaft support structure for supporting an end portion of a pinion shaft engaged with a rack on a rack housing.

  A rack-and-pinion type steering device supports a pinion shaft connected to the lower end of a steering shaft and a rack shaft by a rack housing, and both ends of the rack shaft are connected to a steering device via a tie rod or the like to connect the rack shaft. Turn the wheel according to the left / right movement of the wheel. The pinion shaft is normally pivotally supported through two rolling bearings at both ends of the pinion forming portion, that is, at the connecting portion side between the lower shaft end and the steering shaft. Generally, at least one of the two bearings that support the pinion shaft is a deep groove ball bearing, which restricts the axial movement of the pinion shaft.

Patent Document 1 discloses a pinion shaft that is supported by a ball bearing on the pinion shaft insertion port side of the rack housing.
In Patent Document 1, a four-point contact deep groove type ball bearing is provided at the pinion shaft insertion port of the rack housing, and the outer ring of this ball bearing is restrained by the inner peripheral step portion of the housing insertion port and the threaded cover. The bearing inner ring is restrained in the axial direction by a ring in which a stepped shoulder portion of the pinion shaft and a circumferential notch groove of the shaft are caulked and fitted. In order to avoid stress concentration in the notch groove based on bending stress and torsional force applied to the pinion shaft, a plurality of stress distribution grooves are provided in the vicinity of the notch groove to engage with the ring. Yes.

Further, Patent Document 2 shows a pinion shaft whose end is supported by a ball bearing.
JP 2007-112272 A Japanese Patent Laid-Open No. 11-43056 (Patent No. 3891646)

  In this type of rack-and-pinion type steering device, the pinion shaft is subjected to excessive external force or rotational bending stress due to the rotation of the pinion shaft during a vehicle collision or running on a poor road surface. To do. In addition, it is necessary to fix the inner and outer rings of the ball bearing from both end surfaces in order to securely restrain the pinion shaft in the axial direction by eliminating the axial backlash. The ball bearing to be fitted to the shaft end portion of the pinion shaft A stepped portion is formed as the axial receiving surface. There is a problem in that the stepped portion is subjected to a compressive force due to a bearing reaction force and a tensile / compressive rotational bending stress due to rotation of the pinion shaft, resulting in fatigue failure.

  In particular, in an electric power steering device, since the worm wheel is provided on the pinion shaft, the ball bearing is often arranged on the tip end side of the pinion shaft, and the bearing support position of the pinion shaft is regulated by the vehicle layout, and the input side Compared with the rack, since it is disposed at a position relatively close to the meshing center with the rack, the reaction force applied to the bearing during torque loading tends to be larger than that on the input side.

  Furthermore, because the stepped part of the pinion shaft is subjected to tension / compression rotational bending stress amplitude due to the rotation of the pinion shaft, severe conditions are required for fatigue strength. Become prominent. In addition, since initial stress due to nut tightening acts on the stepped portion to fix the bearing, measures for improving fatigue strength such as surface heat treatment cannot be implemented because of fear of delayed fracture.

  The present invention provides a rack-and-pinion type steering that can alleviate the stress concentration generated in the bearing fitting portion at the shaft end of the pinion shaft, and can reduce the compressive stress at the shaft end portion and improve the fatigue strength. An object of the present invention is to provide a pinion shaft support structure of an apparatus.

To achieve the above object, a rack and pinion type steering apparatus according to claim 1 of the present invention includes a rack shaft slidably supported by a rack housing, and a pinion that meshes with the rack of the rack shaft. In a pinion shaft support structure of a rack and pinion type steering apparatus, comprising a pinion shaft and a support mechanism portion that rotatably supports the pinion shaft on the rack housing, the pinion shaft has a pinion shaft at a front end portion of the vehicle. A concave portion that is coaxial with the shaft is formed, and an internal thread portion that is coaxial with the pinion shaft and extends rearward of the vehicle is formed at a central portion of the bottom portion of the concave portion with a smaller inner diameter than the inner peripheral surface of the concave portion. And the female screw portion constitute a bolt hole, and the support mechanism portion rotates the bolt with a bolt and an outer ring supported by the rack housing. And the bolt is a portion between the head on the front side of the vehicle, the male screw portion on the rear side of the vehicle, and the head and the male screw portion. The shaft portion is smaller in diameter and larger in diameter than the male screw portion, and the shaft portion includes a bearing fitting portion on the vehicle front side in which an inner ring of the ball bearing is externally fitted, and more than the bearing fitting portion. A front end projecting toward the rear side of the vehicle, the male threaded portion is screwed into the female threaded portion of the bolt hole, and the front end of the shaft portion is fitted into the inner peripheral surface of the recess by inlay fitting. The bolt is fixed to the pinion shaft .

Furthermore, the pinion shaft support structure of the rack and pinion type steering device according to claim 2 of the present invention is the pinion shaft support structure of the rack and pinion type steering device according to claim 1 , wherein the support mechanism portion is the rack. The ball bearing further includes a threaded lid closing member screwed into an opening at a vehicle front side end portion of the housing, wherein both end portions of the inner ring of the ball bearing are sandwiched between an end portion of the pinion shaft and a head portion of the bolt. outer end portions of the is characterized in that it is sandwiched restraining the rack housing by the threaded cap closure site material.

  According to the present invention, a rack and rack that can alleviate the stress concentration generated in the shaft support fitting portion at the shaft end of the pinion shaft and can reduce the compressive stress at the shaft end portion and improve the fatigue strength. A pinion shaft support structure for a pinion type steering device is provided.

  Hereinafter, the pinion shaft support structure of the rack and pinion type power steering apparatus according to the embodiment of the present invention will be described.

[Embodiment 1]
FIG. 1 is a partial cross-sectional view showing a structure of a pinion shaft support portion of a rack and pinion type steering apparatus according to a first embodiment of the present invention. This figure is a longitudinal sectional view along the longitudinal direction of the pinion shaft. The rack shaft 1 is accommodated in a rack housing 2 fixed to a vehicle body frame (not shown) so as to be axially slidable, and both ends thereof extend from the rack housing 2 and are steered via ball joints and tie rods (not shown). Connected to

  A pinion shaft 3 is accommodated in the rack housing 2 so as to be rotatable and immovable in the axial direction so as to be orthogonal to the rack shaft 1, and the vehicle rear side (steering wheel side) end of the pinion shaft 3 extends from the rack housing 2. It is connected to a steering shaft (not shown). The vehicle front side end of the pinion shaft 3 is pivotally supported by a pinion shaft support mechanism 5 in the rack housing 2. The pinion shaft support mechanism will be described later.

  The rack shaft 1 is supported by the rack guide 6 at a position crossing the pinion shaft 3 (the surface opposite to the rack forming surface), and is screwed to the rack guide accommodating portion 2a of the rack housing 2 on the outer periphery. A cup-shaped lid body 7 having a portion is screwed. A compression spring 8 is disposed between the cup-shaped lid 7 and the rack guide 6, and the rack 1 a of the rack shaft 1 is connected to the pinion 3 a of the pinion shaft 3 via the rack guide 6 by a spring force of the compression spring 8. Engage with pressing force. This pressing force can be adjusted by changing the screwing position of the cup-shaped lid 7 with respect to the rack housing 2.

  An inlay portion 9 having a concave axial center is formed on the shaft end surface of the tip portion of the pinion shaft 3, and an internal thread portion 10 is formed in alignment with the axial center, and a bolt 11 is screwed into the internal thread portion 10. It is. In addition, the inner diameter part of the spigot part 9 is formed in a state aligned with the axial center and the outer peripheral part of the pinion shaft 3, that is, in a concentric state, and the spigot part 9 and the bolt shaft part 13 have a fine fit.

  The bolt 11 has a shaft portion 13 having a diameter larger than that of the male screw portion 12 and a bolt head portion 14 having a diameter larger than that of the shaft portion 13 following the male screw portion 12 formed at the tip. An inner ring 16 of a ball bearing 15 is fitted to the shaft portion 13 of the bolt 11, and an outer ring 17 of the ball bearing 15 is fitted to an inner diameter portion of the pinion shaft insertion end opening of the rack housing 2. Further, a threaded lid closing member 18 having a male threaded portion on the outer periphery is screwed into the end opening of the rack housing 2. One end surface of the outer ring 17 of the ball bearing 15 abuts on a step portion 19 of the pinion shaft insertion end opening of the rack housing 2, and the other end surface of the ball bearing outer ring 17 is a lid closing member screwed into the rack housing 2. The inner end of 18 is pressed.

  Next, although there is a part which overlaps with the above, if the assembly procedure of the pinion shaft support structure of the illustrated embodiment is briefly described, the ball bearing 15 is first fitted to the shaft portion 13 of the bolt 11 in advance. Prepare in the state. Then, the bolt 11 having the ball bearing 15 is screwed into the female thread portion 10 at the shaft end of the pinion shaft 3 incorporated in the housing, and the shaft tip end of the bolt 11 is fitted into the spigot portion 9 of the pinion shaft 3. .

  Before and after this, the bolt 11 is screwed into the pinion shaft 3 until the outer ring 17 of the ball bearing 15 contacts the opening step portion 19 of the rack housing 2. By screwing the bolt 11, one outer ring end surface (housing rear side) and one inner ring end surface (bolt head side) of the ball bearing 15 are pressed by the step portion 19 and the bolt head 14 of the housing 2. As a result, a tensile force toward the outer end side acts on the pinion shaft 3, and the pinion shaft outer end surface (the outer end surface connected to the spigot portion 9) comes into pressure contact with the other end surface of the bearing inner ring 16. Thereafter, the lid closing member 18 is screwed into the housing opening to press-contact the inner end thereof with the other end face of the bearing outer ring 17.

  By adopting such a shaft support structure, initial stress is not applied to the stepped portion generated at the fitting portion between the shaft end of the pinion shaft 3 and the shaft portion 13 of the bolt 11, and the pinion shaft side Only the tensile stress due to bolt tightening is applied, the compressive stress is small during operation, and the swing stress amplitude becomes small, and as a result, the fatigue strength can be improved. Since the stepped portion between the head portion 14 and the shaft portion of the bolt 11 is outside the bearing 15, the influence of the bearing reaction force is small.

[Embodiment 2]
The above embodiment is an example applied to a rack and pinion type steering device that does not have a steering assist mechanism. However, the present invention is not limited to such a manual type steering device, but a rack and pinion type as a second embodiment. This is applied to the electric power steering apparatus or hydraulic power steering apparatus. Further, the present invention can be similarly applied to a rotation support structure of a pinion shaft in which other general racks and pinions are engaged.

  As described above, according to the present invention, the bolt is screwed into the shaft end of the pinion shaft that meshes with the rack, and the shaft portion of the bolt is supported by the bearing. Can ease concentration. In particular, the stress concentration at the stepped portion is eliminated by using it in places where there is a concern about stress concentration or insufficient strength at the pinion shaft support portion of the steering device where the pinion shaft frequently rotates forward and backward by steering operation. In addition, the fatigue strength can be improved.

It is a fragmentary sectional view showing the structure of the pinion shaft support part of the rack and pinion type steering device by one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rack shaft 2 Rack housing 3 Pinion shaft 6 Rack guide 9 Inlay part 11 Bolt 13 Bolt shaft part 14 Bolt head 15 Ball bearing 18 Lid closing member 19 Step part

Claims (2)

A rack shaft slidably supported on the rack housing;
A pinion shaft having a pinion that meshes with a rack of the rack shaft;
In a pinion shaft support structure of a rack and pinion type steering apparatus , comprising a support mechanism portion that rotatably supports the pinion shaft on the rack housing ,
A concave portion coaxial with the pinion shaft is formed at a vehicle front side end portion of the pinion shaft, and a vehicle having an inner diameter smaller than an inner peripheral surface of the concave portion and coaxial with the pinion shaft at a central portion of the bottom portion of the concave portion. A female screw portion extending rearward is formed, and the concave portion and the female screw portion form a bolt hole, and the support mechanism portion is supported by the rack housing so that the bolt and the outer ring are rotatably supported. A ball bearing, and the bolt is a portion between the head on the front side of the vehicle, a male screw portion on the rear side of the vehicle, the head and the male screw portion, and has a smaller diameter than the head and The shaft portion is larger in diameter than the male screw portion, and the shaft portion is located on the vehicle front side where the inner ring of the ball bearing is externally fitted, and on the vehicle rear side relative to the bearing fitting portion. A protruding tip portion, and the male screw portion is Pinion shaft the bolt by the end portion of the screwed into the internal thread portion and the shaft portion of the belt holes is spigot fitted to the inner peripheral surface of the recess, characterized in that it is fixed to the pinion shaft Support structure. The support mechanism portion further includes a threaded lid closing member screwed into an opening of a front end portion of the rack housing, and both end portions of the inner ring of the ball bearing are the end portions of the pinion shaft and the heads of the bolts. The pinion shaft support structure according to claim 1 , wherein both ends of the outer ring of the ball bearing are clamped and restrained by a rack housing and the threaded lid closing member.

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